<h1>Polygon and Freehand Contour Drawing Tool</h1>

Use this tool to trace 2D contours on image slices.

<h3>Drawing polygonal contours</h3>
You can draw a polygon by making a sequence of left-clicks with the mouse over the image slice. When you want to close the polygon, right-click.

<h3>Drawing freehand contours</h3>
To draw a freehand segment, hold the left mouse button down and drag the mouse. To finish drawing the segment, release the left mouse button. You can combine freehand segments with polygon segments. To close the contour, right-click.

<h3>Controlling freehand behavior</h3>
In the 'Tool Options' panel, you can control how freehand drawing behaves. Select between <i>continuous drawing</i>, which gives you greatest control, but makes subsequent editing most difficult, and <i>line segment</i> mode, where the freehand contour is build up from straight line segments of specified length.

<h3>Editing contours</h3>
Once the contour has been closed, you can edit it by moving the vertices of the polygon. Drag a selection box over the vertices you want to edit, and then drag the selected vertices to move them.

<h3>Adding contours to the segmentation layer</h3>
A contour is not added to the segmentation layer until you press the <b>accept</b> button. When you accept the contour, its interior is filled with the currently selected drawing label.


